Thermochemistry : SystemSurrExoEndo (4 Variations)
Sulfuric acid is added to water in a beaker and the resulting solution is much warmer than either the water or acid was initially.
Identify the following items as being part of the system or the surroundings, and indicate whether the process is exothermic or endothermic.

Thermochemistry : BombCalorimeter (4 Variations)
Stearic acid (CH3(CH2)16CO2H) is a fatty acid, the part of fat that stores most of the energy. 1.00 g of stearic acid was burned in a bomb calorimeter. The bomb had a heat capacity of 652 J/oC and a 500. g water reservoir. If the temperature rose from 25.0 to 39.3 oC, how much heat was released when the stearic acid was burned?

Thermochemistry : CoffeeCupCalorimeter (2 Variations)
A block of copper is heated to {x} °C and then is dropped into a coffee cup calorimeter containing {y} g of water at 25.0 °C. The final temperature of the system is 45.1 °C. What is the mass of the copper block to the nearest gram? (Assume all heat is transferred to the water). Write your answer in the box, and do NOT include units.

Specific heat capacity of copper = 0.383 J/(g*°C)

Specific heat capacity of water = 4.18 J/(g*°C)

Calorimetry / Thermochemistry |

Chemometrics

Thermochemistry : FuelAmpWattHeat (4 Variations)
Gasoline has an enthalpy of combustion of approximately 24000 kJ/gallon. When gasoline burns in an automobile engine, approximately 30% of the energy released is used to produce mechanical work. The remainder is lost as heat transfer to the engine's cooling system and eventually the atmosphere. As a start on estimating how much heat transfer is required, calculate what mass of water could be heated from 25 to 100oC by the combustion of 1.0 gallon of gasoline in an automobile.

Consider the graph above. Which of these substances has the highest specific heat capacity?

Calorimetry / Thermochemistry |

Heat Capacity

Thermochemistry : HeatCapacityLiq (4 Variations)
100 g of water (c=4.184 J/g.oC), 100 g of ethanol (c=2.46 J/g.oC), 100 g of carbon tetrachloride (c=0.861 J/g.oC), and 100 g of ethylene glycol (c=2.42 J/g.oC) at 50oC were each placed into a separate coffee cup calorimeter and the temperature recorded. The temperature of the surroundings was 20oC. After one hour the temperature of which substance would have changed by the largest amount? Assume that the rate of heat transfer from the coffee cup to the surroundings was the same in each case.

In an experiment, 50 g of a metal was heated to 100oC and placed in 200 g of a liquid at 25oC. Which of the following combinations of metal and liquid will produce the largest temperature increase in the liquid? (Assume that there is no transfer of energy to the surroundings.)

Calorimetry / Thermochemistry |

Heat Capacity

Thermochemistry : CalcHHessLaw (8 Variations)
The industrial process for making sulfuric acid has three steps. Using the data given, calculate the enthalpy change for the overall reaction for the process (the equation is given below).

In an experiment a block of aluminum was heated to 100oC and placed in 200 g of water at 25oC. If the final temperature of the system is 43oC, and no heat transfer to the surroundings occurred, what is the mass of the aluminum block?

Thermochemistry : PhaseChanges (8 Variations)
Steam at 100oC is condensed by an ice-water mixture at 0oC. Assuming that there is still ice present when the process is over, how much ice will be melted if 10.0 g of steam is condensed? The following may be useful:enthalpy of vaporization of water = 40.7 kJ/mol; enthalpy of fusion of water = 6.07 kJ/mol; specific heat capacity of water = 4.184 J/g•K.

If you perform this reaction and collect the following table of data, in which trial(s) is AgOCN clearly the limiting reactant?

Trial

AgOCN used

NH4Cl

AgCl produced

1

20.4 mL

5.3 mL

2.4 g

2

20.3 mL

10.4 mL

4.3 g

3

20.6 mL

15.4 mL

6.2 g

4

20.5 mL

20.6 mL

8.2 g

5

20.4 mL

25.2 mL

10.2 g

6

20.3 mL

30.4 mL

10.3 g

The mL of AgOCN and NH4Cl are the initial amounts used, the mass of AgCl is how much was recovered from the reaction. (Hint: You do not need to do any calculations to answer this question.)

Stoichiometry

Gases : VolGasReactInTorch (10 Variations)
Oxyacetylene torches used in high-temperature welding use a combination of oxygen and acetylene. The combustion of acetylene (C2H2) occurs in these torches. What volume of oxygen is needed to react with 250 mL of acetylene?

When 0.1 moles of zinc is reacted with 0.1 moles of hydrochloric acid ...

Stoichiometry |

Reactions

Stoichiometry : TheorYieldDeviation (10 Variations)
You reacted a known amount of phosphorous triiodide with excess water and determined that the percent yield of phosphoric acid was less than 100%, which of the following statements could explain why?
PI3 + 3H2O H3PO3 + 3HI

Stoichiometry |

Reactions

Stoichiometry : CalcWtPercent (6 Variations)A standard dose of antacid as a calcium supplement is two tablets. The active ingredient in many of these tablets is calcium carbonate. One tablet, having a weight of 1.415 g, is reacted with excess HCl(aq) to produce 0.22 g CO2. What is the weight percent of calcium in this tablet?

CaCO3(s) + 2HCl(aq)CaCl2(aq) + H2O(l) + CO2(g)

Stoichiometry |

Chemometrics

Stoichiometry : CalcPercentPurity (4 Variations)
To test the purity of calcium sulfate, you dissolve a 4.56g sample in water and add oxalic acid to precipitate out calcium oxalate. If 3.45g of precipitate forms, what is the percent purity of the calcium sulfate?

Stoichiometry : CombustionAnalysis (10 Variations)
While working in the lab, you find a bottle of white powder labeled
"analgesic compound #5". Since the original investigator neglected
to record the identity of the substance, you decide to perform a
combustion analysis to identify the compound. You have a 65.7 g
sample that when burned produces 182 g CO2 and 51.7 g
H2O. What is the formula of this compound? (The compound
only consists of C,H, and O.)

Stoichiometry |

Molecular Properties / Structure

Stoichiometry : ExplainYldError (4 Variations)
Your TA gives you an aqueous solution containing an unknown quantity of AgNO3(aq) and an unknown quantity of Mg(NO3)2(aq). You are asked to determine the molarity of Ag+ in the solution. You add HCl(aq) to your unknown to precipitate the silver as AgCl(s), then filter out the precipitate, dry it, weigh it, and calculate the concentration of silver ion. However, your TA tells you that your calculated value of [Ag+(aq)] is lower than the actual value. Which of the following could account for your answer being too low? There may be more than one correct answer.

Stoichiometry |

Reactions |

Chemometrics

Stoichiometry : FormulaFromComp (8 Variations)
Lactic acid is the substance that makes your muscles burn when you've been exercising hard. Lactic acid is composed of 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by weight. If it has a molar mass of 90 g/mol, what is its molecular formula?

Stoichiometry |

Molecular Properties / Structure

Stoichiometry : PrecipYield (3 Variations)
In a laboratory experiment to determine accurately the amount of barium in solution, aqueous sulfuric acid was added to the solution to precipitate barium sulfate, which was then filtered and weighed. In this experiment it is MOST important that ...

Stoichiometry |

Reactions |

Chemometrics

Bonding : DetermineStructure (8 Variations)H
A substance is analyzed and found to contain 57.10% carbon, 4.80% hydrogen and 38.06% oxygen by weight. Its molecular weight is determined to be 126.11 g/mol. Which of the structures shown are possible structures for the substance?

Stoichiometry : RxnMolsProduced (8 Variations)
Given the following balanced chemical reaction:
4A + 3B2 2A2B3
If 12 moles of A are reacted with excess B2, how many moles of A2B3 will be produced?
Very carefully enter the number below.

Complete the reaction table for a reaction mixture containing 12.0 moles of iron and 10.0 moles of oxygen, and select the true statement(s) from following list.

Stoichiometry |

Reactions |

Chemometrics

Stoichiometry : SolnStoich (4 Variations) You are working in a forensic lab and are given a blood sample from a suspected drunk driver and asked to determine the person's blood alcohol level. The legal limit is 0.08% by mass in most states. You use the following reaction in your determination, assuming only the ethanol (C2H5OH) in the blood sample will react with the dichromate. 16H+(aq) + 2Cr2O72-(aq) + C2H5OH(l)4Cr3+(aq) + 11H2(l) + 2CO2(g)

If 14.6 mL of 0.10 M K2Cr2O7 are needed to react completely with 28 g of blood, what is the blood alcohol level of the driver?